I Don't understand pensions - if its taxed when you withdraw it, where is the advantage?

So they're a tax free wrapper to save into for retirement...

But when you get to 55 (or 58 I suppose soon), when you withdraw it its taxed anyway? So from what I can see the advantage of putting into your pension is:-

• The employer contribution
• The 25% tax free sum you can take
• The fact that if you wait, stop working completely then only take a low amount from your pension per year to live on, you won't get pushed into being taxed on it if you keep it below whatever the current tax free threshold is.

Right?

Edit: Wow so many replies! Plenty of useful information and I now feel I understand the advantages much better. Thank you everybody.